It's almost certainly the power supply. Most consist of just a bridge rectifier and capacitive dropper, some of which are so bad as to negate some of the advan

It's almost certainly the power supply. Most consist of just a bridge rectifier and capacitive dropper, some of which are so bad as to negate some of the advantages of the LED's efficiency. Poor design and cheap components are the norm, so you get lots of failed diodes and capacitors. They also have terrible power factor, though that isn't much of a concern for consumers.